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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="4-1.js"></script>
    <style></style>
  </head>
  <body>
    <div class="d1">
      <div class="d2"></div>
    </div>

    <script>
      var a = [1, 2, 3];
      var b = [];
      a.forEach((data, index) => {
        b[index] = data;
      });
      b[0] = 0;
      console.log(a);
      console.log(b);

      console.log("----------------------------------");

      function F1() {
        
      }
      F1.prototype.showhello = function()
{
  alert('hello')
}
      function f1(){}
      f1 = new F1()

      var f11 = new f1()

    f11.showhello()      
      
    </script>
  </body>
</html>
